1. Field of the Invention
The present invention relates to a cone crusher used to crush rocks, ores and the like.
2. Description of the Related Art
In a cone crusher in which a truncated-cone shaped mantle is eccentrically rotated within a conical cylindrical concave fit in an upper body of a machine body to press and crush raw materials such as rocks, ores and the like supplied from the top between the concave and the mantle, a lower clearance at which the rotating mantle moves closest to the concave is called an outlet clearance (on the closed side), the outlet clearance determining a crashing size. A structure for changing and adjusting the outlet clearance are roughly grouped into two types as follows.
In one type, the mantle side is moved by a hydraulic mechanism to change the outlet clearance. In this type of cone crusher, as shown in FIG. 3A, a head center (32a) of a main shaft (32) having a mantle (33) mounted thereon is vertically moved by a piston rod (35a) of a hydraulic cylinder (35) the hydraulic cylinder 35 is provided within the main shaft (32) to change an outlet clearance .alpha. between the mantle (33) to change (34) fitted within an upper body (31a) of a machine body (31). Further, in the cone crusher of this type, as shown in FIG. 3B, a magnetic strain type stroke detection device (36) is disposed under the hydraulic cylinder (35), and a moving amount of the piston rod (35a), which is a height position of the mantle (33), is detected by the stroke detection device (36) whereby the operation of the hydraulic cylinder (35) is controlled to remotely change and adjust the outlet clearance .alpha..
In the other type, a concave side is moved by a screw mechanism to change the outlet clearance. In this type of cone crusher, as shown in FIG. 4A, a concave support (45) having a concave (44) fit internally thereof is rotatably threadedly fit in a cylindrical upper body (41a) fixedly arranged at the upper part of a machine body (41), and the concave support (45) is rotated and vertically moved to change the outlet clearance .alpha. between the concave (44) and a mantle (43) mounted on a main shaft (42). As a method for rotating the concave support (45), a method has been heretofore often employed in which a plurality of pressure receiving rods (45a) provided equidistantly on an upper outer circumference of the concave support (45) are pressed and rotated by a plurality of hydraulic cylinders (46) rotatably arranged at the upper part of the upper body (41a), as shown in FIG. 4B. Recently, however, a method has been proposed and put to a practical use in which a gear (47) is mounted on an upper outer circumference of the concave support (45), a driving device (48) having a wide pinion (48a) meshed with the gear (47) is disposed at the upper part of the upper body (42a), and the concave support (45) is rotated by the driving device (48), as shown in FIG. 4C.
Incidentally, in these types of cone crushers, as the crushing repeatedly proceeds, abrasion of the concave and mantle increases to enlarge and change the outlet clearance for determining the crushing size. Accordingly, the crushing size changes and the yield of good product lowers unless the outlet clearance is adjusted not only at the time of assembly and at the time of initial operation, but also at the time after operation for a certain period of time.
On the other hand, recently, with a severer demand of quality on the user's side, the importance of adjustment of the crushing size, which is the outlet clearance, has risen. Further, for the purpose of continuing a stable operation, it is also necessary to detect on abrasion amount of the concave and mantle to replace them at an adequate time. It is important to know a changing value of the outlet clearance in order to change and adjust it at an adequate time.
However, in the conventional cone crusher employing the latter type as described above, there is no function to detect the height position of the concave, that is, the outlet clearance. Thus the conventional cone crusher has a problem in that one cannot but employ relatively cumbersome and inaccurate methods such as a method in which for changing and adjusting the outlet clearance, the size of crushed articles is periodically measured, and the adjusting time and amount are set from the change of the crushing size, and a method in which in changing and adjusting it, a lead ball is inserted into a part on the closed side between the concave and the mantle to crush it whereby the outlet clearance after adjustment is assured.
From a viewpoint of the above, the present inventors have filed, prior to the instant application, a Japanese patent application for a cone crusher having an improved construction in which a moving amount of a concave which is vertically moved by a screw mechanism whereby an outlet clearance between the concave and a mantle and abrasion amount thereof can be measured, and the outlet clearance can be remotely changed and adjusted on the basis of the measured value (Japanese Patent Application LaidOpen No. 154630/1994).
In the cone crusher according to the aforementioned prior application, as shown in FIG. 2 which is an explanatory view of a schematic construction thereof, a concave support (25) having a concave (24) fit internally thereof is rotatably threadedly fit within an upper body (21a) of a machine body (21), an annular large gear (25b) is mounted on an outer periphery of an upper cover (25a) provided on the concave support (25), and a wide pinion (26a) of a driving device (26) disposed on the outer periphery of the upper body (21a) is meshed with the large gear (25b) whereby the concave support (25) is rotated by the driving device (26) so that the concave support (25) is vertically moved to change and adjust an outlet clearance .alpha. between the concave (24) and a mantle (23) mounted on a main shaft (22).
The driving device (26) is constructed such that the pinion (26a) is mounted on an outlet shaft of a driving motor (26b) having a torque limiter coupling (26c) interposed therein, the driving motor (26b) being connected to an external control device (29). A rotation detection device (27) for detecting a rotation of the pinion (26b) is disposed at the upper part of the driving device (26), the rotation detection device (27) being connected to an external operation display device (28), which is in turn connected to the control device (29) of the driving device (26).
On the other hand, the operation display device (28) has a function to process an electric signal output from the rotation detection device (27) in accordance with a conversion program to index a rotational frequency of the concave support (25), to operate a vertical moving amount from a reference height position, and to operate an outlet clearance .alpha. from an angle of inclination between the mantle (23) and the concave (24) known previously and the above-described moving amount, these values being stored erasably and displayed.
In the above-described prior cone crusher, in the remote control of the driving device, the concave support is moved down until the mantle and the concave come into contact on the closed side, after which they are moved upward equally to the value of the set outlet clearance on the basis of processed data by the operation display device.
However, in the above-described prior cone crusher, the operating property of the actual operation thereof was studied in more detail, as a result, we found that the following problem remained as a problem to be solved.
That is, in this cone crusher, in the initial setting of and in the resetting of the outlet clearance, the concave is moved down until the mantle and concave come into contact, and a stop height position thereof is input as a zero position of the outlet clearance at the initial setting and resetting into the operation display device to grasp the setting of the outlet clearance and the abrasion amount. In this case, the contact between the mantle and the concave is detected in such a manner that the rotation of the pinion of the driving device stops due to the contact therebetween and an output value from the rotation detection device is zero. At this time, the torque limiter coupling of the driving device slips so that the pinion ceases to rotate, which is detected by the stop of the driving motor.
On the other hand, when the mantle and concave come to contact by the downward movement of the concave support, a clearance between the concave support and the threads disappears and they become fastened to each other. Therefore, when the driving motor is stopped when the torque limiter coupling slips, the torque of the set value of the torque limiter coupling is applied as a thread tightening force, and in addition, an inertia force at the time when the concave support being rotated stops is also applied as a tightening force. Therefore, the concave support and the threads of the upper body are fastened with an excessively large force.
Therefore, it is necessary to reverse the driving motor to move the concave support upward to disengage the tightening between the concave support and the upper body. However, since the tightening force therebetween already exceeds the set torque, there gives rise to an inconvenience that the outlet clearance cannot be set unless the tightening force for rotating the concave support is released.
Accordingly, in order that the setting of the outlet clearance following the setting of the zero position of the outlet clearance due to the contact between the mantle and concave is carried out to improve the operating property, it is necessary to detect the contact between the mantle and the concave to stop the operation of the driving device before the operation of the torque limiter coupling, that is, before a surplus tightening force in excess of the set torque occurs between the concave support and the upper body.